Process for the application of fittings to waveguides

ABSTRACT

In order to allow the use of standard fittings with a hollow waveguide of noncircular inner perimeter and walls whose thickness varies along its cross section profile, the inner perimeter is widened or enlarged to a desired inner crosssectional dimension for a distance of approximately one wavelength by inserting a preformed plug having the desired cross-sectional shape and dimensions.

United States Patent 11 1 schuttloffel 14 1 Nov. 20, 1973 [54] PROCESS FOR THE APPLICATION OF 2,595,541 5/1952 Riordan 82/4 3 X FITTINGS To WAVEGUIDES 2,535,470 12/1950 Welshman 3,540,329 11/1970 Gill Inventor: Erich Schutfloffel, Backnang, 3,149,295 9/1964 010116 Germany 3,381,370 5/1968 Goonan et al. 2,743,322 4/1956 Pierce et al.... [73] Asslgnee. Llcentia Patent-Verwaltungs-GmbI-l, 3,050,701 8/1962 Tang 0 Frankfurt am Mam, Germany 3,388,352 6/1968 1211111011111... 2 F F 2 Rooney l 2] "F eb 19 3,500,264 3 1970 Floyd 333/98 R [21] Appl. No.: 7,861

Primary ExaminerCharles W. Lanham Assistant ExaminerRobert M. Rogers [30] Foreign Apphcat on Prlonty Data Anomey spencer & y

Feb. 1, 1973 Germany P 19 04 993.5 7

52 us. Cl. 29/600, 29/237, 333/98 R [57] ABSTRACT 51 1111. C1. H0lp 11 00 In Order to allow the use of Standard fimngs Wlth a [58] Field of Search 29/237, 600, 601; hollow Waveguide of noncirwlar inner Peri!eter and 72/370; 82/43; 144/205; 333/95, 98 walls whose thickness varies along its cross section profile, the inner perimeter is widened or enlarged to [56] References Cited a desired inner cross-sectional dimension for a dis- UNITED STATES PATENTS tance of approximately one wavelength by inserting a 1 2 7 I0 9 M u l 82 4 3 preformed plug having the desired cross-sectional 1'783'088 11/1930 Shape and dimensions 2,357,748 9/1944 Lyon 72/370 X 4 Claims, 5 Drawing Figures PATENTED NOV 2 0 I975 V INVENTOR Erich Schilafllffel Figga Fig.5

ATTORNEYS.

PROCESS FOR THE APPLICATION OF FITTINGS TO WAVEGUIDES BACKGROUND OF THE INVENTION This invention relates to flexible hollow waveguides having a noncircular inner perimeter or cross section and walls whose thickness varies along its crosssectional profile. More particularly, this invention relates to a method of modifying the ends of such waveguides so that standard fittings may be affixed thereto.

Recently, flexible waveguides consisting of a preferably seamless, drawn metal tube having a noncircular inner perimeter or cross section, which is usually rectangular or elliptical have become known. In order to prevent undesired deformation of the inner surface of the waveguide during bending and/or twisting thereof, the walls of the waveguide are constructed so that their thickness varies along the cross-sectional profile of the waveguide. Examples of such waveguides are disclosed in. applicants copending US. Pat. applications Ser. Nos. 745,578 (now U.S. Pat. No. 3,585,540) and 856,271 now US. Pat. No. 3,603,905, filed july 17, 1968, and Sept. 9, 1969, respectively. As with most waveguides, to use such flexible waveguides, appropriate fittings are required. In order to mount these fittings to the waveguide, suitable grooves are cut in the ends of the waveguide which grooves serve for fastening purposes, i.e., to fasten the fitting to the waveguide. However, as a result of the manufacturing process for these flexible waveguides, the deviations of the inner perimeter from the prescribed or desired dimensions are relatively great, often resulting in impedance mismatches and mounting difficulties when attempting to utilize a standard fitting, i.e., a fitting with standard dimensions and electrical characteristics, with such waveguides. To eliminate these problems, the required fitting thus must be individually produced or manufactured according to the dimensions of the particular waveguide train being utilized, or a fitting of standard dimensions must be specially modified or adapted to the dimensions of the .waveguide. Both of these alternatives are, of course,

time-consuming and expensive.

SUMMARY OF THE INVENTION It is accordingly the object of the present invention to avoid the above-mentioned disadvantage of requiring fittings which are individually manufactured or adapted to a particular train or string of waveguide by providing a relatively simple method of modifying the end of a section of flexible hollow waveguide of the above type so that a standard fitting may be utilized therewith.

In accordance with the invention, the abovementioned disadvantages are eliminated by, prior to the application of a standard fitting, slightly widening or expanding the inner perimeter of the end of the flexible waveguide for a distance or area along the length thereof of approximately one wavelength to provide a desired or nominal cross section at the end of the waveguide.

The widening of the end of the waveguide is advisably only about one to two millimeters in order that the electrical values or parameters of the waveguide be practically unchanged. To perform the widening, a prefabricated plug of the desired cross section is driven into the end of the waveguide for the approximately one wavelength distance. The widening of the end of the waveguide in this manner results in a conical or tapered line transformer i.e., a transition piece being provided at the end thereof which transforms the cross section of the waveguide with its unpredictable tolerances into a prescribed nominal or standard cross section. Accordingly, an unequivocal or known reference surface and characteristic impedance is provided at the end of the waveguide for the required waveguide fittings which is independent of the manufacturing tolerances for the waveguide fabrication process. The standardization of the tolerances of the waveguide at the end thereof makes it possible to use a single fitting of standard tolerances for all manufactured lengths of such waveguides so that the costs of manufacturing and applying the fittings to the waveguide are reduced. Additionally, the method has the further advantage that the manufacturing costs of the waveguide itself are reduced since a wider range of tolerances during the fabrication thereof is now permissible.

According to a further advantage of the method, the prefabricated setting plug utilized to expand the end of the waveguide is so constructed that after expanding the waveguide, the plug is used to hold or support the device which produces the grooves in the waveguide which serve to fasten the waveguide fittings.

With the aid of the method according to the present invention, it is thus possible to apply or mount the required waveguide fittings at the installation location in a relatively simple manner and with an accuracy which satisfies all of the electrical requirements and eliminates the need for expensive specially produces fittings and/or individual electrical balancing thereof with the waveguide.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an end view of a flexible waveguide of the type with which the method according to the invention is concerned.

FIG. 2 is a sectional view of a diametral plane extending through a waveguide and a connector being shown in a tilted position.

FIG. 3 is a sectional view showing the fitting or connector in its engaging position.

FIG. 4 is a side view of one end of a waveguide formed with grooves for locking with the fitting or connector.

FIG. 5 is a sectional view of a device for cutting the grooves and for beat in the tapered plug into the waveguide.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 11, there is shown the end of a flexible waveguide 40 having a noncircular inner perimeter or cross section 41, i.e., the inner perimeter is of generally rectangular shape. In order to prevent an undesired deformation of the inner perimeter 41 during bending and/or twisting of the waveguide, either during use or during shipment or handling, the wall 42 of the waveguide has a thickness which varies along its crosssectional profile. In the particular waveguide configuration illustrated, the thickness of the wall 42 of the waveguide 40 is thinner in the regions indicated by the reference numerals 44 47 along the two principal axes of the waveguide than it is in the remaining portions of the wall including the corners. Such a construction results in a waveguide which is equally pliable in the planes of the two principal axes of its cross section. It is to be understood, however, that the invention is not limited to a flexible waveguide having this type of cross section, but can be utilized with waveguides having other varying wall thickness corss-sectional profiles.

In order to widen or expand the inner perimeter 41 of the waveguide 40 to provide it with a desired or reference cross section according to the invention so that fittings of standard dimensions may be mounted thereon, a prefabricated tapered plug 30 (see FIG. having a cross section corresponding to that of the inner perimeter 41 of the waveguide, and of the desired dimensions, is driven into the end of the waveguide for a distance of approximately 1 wavelength. The resulting expansion of the inner perimeter 41, which as indicated above, should not be greater than about one to 2 millimeters in order to leave the electrical characteristics of the end of thw waveguide practically unchanged, results in the formation ofa conical line transformer or transition piece in the end of the waveguide. Thereafter, the grooves 5 and 7 (FIGS. 2-4) which serve to fasten the connectors or fittings to the end of the waveguide are cut into the waveguide. Preferably, these grooves 5 and 7 are formed by means ofa cutting device which may be attached to the prefabricated plug 30.

FIGS. 2 to 4 show a waveguide 40 which has upper grooves 5 and lower grooves 7 cut in its exterior adjacent one of its ends. A connector element 3 has a tubular portion formed to fit about the exterior of the waveguide. lts interior is formed with faces 14, 14' which are parallel to an axis 18 which is offset at an angle with respect to the axis 16 of the connector element. These surfaces have an appropriate shape to permit a tilting movement of the connector 3 relative to the waveguide 40 when it is placed about it.

An upper ledge 4 is formed in the form ofa rib which protrudes from the interior of the connector. It is of appropriate shape to engage within the upper groove 5. The lower end of the surface 14 is formed as a ledge 8 to serve as a pressure surface for engaging a corresponding surface within the lower grooves 7.

The surfaces 14 and 14' are formed so as to be generally parallel to an axis 18 which is offset at an angle to the axis 16 of the tubular portion 15 of the connector 3. These surfaces are shaped so that the contact surface 6 between the upper groove 5 and the lower groove 7 serves as the pivot point for tilting movement of the connector. The lower groove 7 is wider, in an axial direction than the upper groove 5 in order to provide sufficient room for the necessary tilting movement.

In use a connector 3 is fitted over the end of the waveguide 40 with the connector in a tilted position and the tilted axis 18 of the connector aligned with the waveguide axis 17. This permits the ledge 4 to pass the contact surface 6 and other waveguide surfaces which are aligned with the exterior of the waveguide. Thereafter the waveguide is tilted so that ledge 4 and the ledge 8 can enter into the grooves 5 and 7, respectively.

The FIG. 5 is a sectional view of a device for cutting the grooves 5 and 7 on the outside of the waveguide 40. It consists shematically of a housing 31 fixed towards the end of the waveguide 40. In this housing the tapered plug 30 is supported. With the aid of a power take-up reel 32 it is possible to drive the plug 30 into the waveguide 40 producing a conical line transformer in the end of that waveguide. The length of the tapered plug 30 is choosen one wavelength A.

On the housing 31 there is attached a device 34 for cutting the grooves 5, 7 into the waveguide 40. This device 34 consists of a milling tool 33. The driving shaft 35 may lead to any driving mechanism.

It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.

I claim:

1. A method of providing a nominal or desired cross section, and thereby a desired characteristic impedance, for the end ofa flexible hollow waveguide which has been drawn from a seamless tube and has a noncircular inner perimeter and walls whose thickness varies along its cross-sectional profile so that fittings of a standard design and dimensions and without modification thereof may be affixed to the end of the waveguide comprising the steps of: prior to affixing the fittings to the end of the waveguide at the point of installation of the waveguide, slightly expanding the inner perimeter of said end of said waveguide for a distance of approximately one wavelength so that the expanded portion constitutes a conical line transformer by inserting a tapered plug of the desired cross section into the said end of said waveguide fastening a groove cutting device to said plug while said plug is in said waveguide; and utilizing said groove cutting device to cut one or more grooves, which serve to fasten a fitting to the end of said waveguide, in the wall of said waveguide.

2. The method of claim 1 wherein the inner perimeter of the waveguide is expanded by about 1 to 2 millimeters.

3. The method of claim 1 wherein the waveguide is drawn from a seamless aluminum tube and has a crosssectional profile which is substantially rectangular with all corners rounded and a wall which is thinnest in the regions along the two principal axes and thickest at the rounded corners.

4. A section of flexible hollow waveguide which is seamless and formed of aluminum and has a crosssectional profile which is substantially rectangular with all corners rounded and a wall which is thinnest in the regions along the two principal axes and thickest at the rounded corners, the inner perimeter of at least one end of said section being slightly expanded and tapered inwardly for a distance of approximately one wavelength so that said expanded portion constitutes a conical line transformer and said at least one end of said section has a desired cross-sectional surface whereby fittings of standard dimensions and electrical characteristics may be affixed thereto.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,772,771 DatedNOVember 20th, 1973 Inventor(s) Erich Schfittlbffel It is certifiedthat error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the heading of the patent, line 10, change "Feb. 1, 1973" to --Feb. 1, l969-. Column 1, line 22, change "july" to -July--. Column 3, line 5, change "corss-sectional" to -cross-sectional; line 19, change "thw" to -the-'.

Signed and soaled this 16th day of April 1971;.-

(SEAL) Attest: I I

EDWARD I'LELETGHERJR; C. WIT- SHALL IJANN Attesting Officer Commissioner, of Patents FORM PO-IOSO (10-69) I USCOM'WDC 60376-P69 fi U.S. GOVERNMENT PRINT NG OFFICE: I969 0866-33l, 

1. A methoD of providing a nominal or desired cross section, and thereby a desired characteristic impedance, for the end of a flexible hollow waveguide which has been drawn from a seamless tube and has a noncircular inner perimeter and walls whose thickness varies along its cross-sectional profile so that fittings of a standard design and dimensions and without modification thereof may be affixed to the end of the waveguide comprising the steps of: prior to affixing the fittings to the end of the waveguide at the point of installation of the waveguide, slightly expanding the inner perimeter of said end of said waveguide for a distance of approximately one wavelength so that the expanded portion constitutes a conical line transformer by inserting a tapered plug of the desired cross section into the said end of said waveguide ; fastening a groove cutting device to said plug while said plug is in said waveguide; and utilizing said groove cutting device to cut one or more grooves, which serve to fasten a fitting to the end of said waveguide, in the wall of said waveguide.
 2. The method of claim 1 wherein the inner perimeter of the waveguide is expanded by about 1 to 2 millimeters.
 3. The method of claim 1 wherein the waveguide is drawn from a seamless aluminum tube and has a cross-sectional profile which is substantially rectangular with all corners rounded and a wall which is thinnest in the regions along the two principal axes and thickest at the rounded corners.
 4. A section of flexible hollow waveguide which is seamless and formed of aluminum and has a cross-sectional profile which is substantially rectangular with all corners rounded and a wall which is thinnest in the regions along the two principal axes and thickest at the rounded corners, the inner perimeter of at least one end of said section being slightly expanded and tapered inwardly for a distance of approximately one wavelength so that said expanded portion constitutes a conical line transformer and said at least one end of said section has a desired cross-sectional surface whereby fittings of standard dimensions and electrical characteristics may be affixed thereto. 